of bridgeport



Patented Apr. 14, 1925.

' To all whom it may concern:

Be it known that I, FREDERICK C. STAN- Y UNITED STATES 1,533,216 PATENT OFFICE.

FREDERICK C. STANLEY, OFBRIDGEPORT, CONNECTICUT, ASSIGNOR T RAYBESTOS COM PANY, OF BRIDGEPORT, CONNECTICUT, A CORPORATION OF CONNECTICUT.

"r noonss OF MAKING rnrorro'n' memos AND :enonocr.

No Drawing. Application filed September 24, 4919, Serial No.' 325,913. Renewed October 28, 1821.

' LEY, a citizen of the United States, residing in the city of Bridgeport, 'county of Fair field, and State of Connecticut, haveinvented certain new and useful Improvements in Processes of Making ,Friction Facingsand Products, ofwhich tlie followin is a specification.

his invention relates to improvements in process of making friction facings and refers more particularly to a clutch facing orabrake lining adapted for use in motor vehicles.

The invention is directed to a novel proc- "ess of making a friction facing from felted unwoven asbestos fibre saturated with a binder.

The object of the invention is to provide a process by which the friction facing has a' maximum tensile strength and hardness so that it can withstand the shocks to which these faeings are subjected in a motor car and also will have suflicient resistance to abrasion; while at the same time it has the proper coefficient of friction. It is also nec-' essary that the binder in these facings must be unaffected by oil or water in use, which object is accomplished by the present invention without in an way detracting from the other characteristics.

The process may be carried out as follows: asbestos fibre preferably the short or low grade fibre is first ground in a'suitable grinding machine or cutter.v The ground material is then put into a beater mixed with the water or other solution and beaten into a pulp. The pulp is then delivered to a paper making machine as for example a wet board machine and formed into sheets or boards of suitable width and thickness.

' This forms an unwoven felted sheet.

Serial No. 511,103.

tion desired. In other words, if the coeflicient of friction must not be materially affected the minimum amount of graphite is used, If the co-eflicient of friction however is not so important, the larger amount may be used and even more than five percent may be used. -There is also mixed with the pulp in the beater an oxidizing agent, as for example red oxide of lead. In using red lead as an oxidizing agent, the amount employed is approximately 1.6 percent by the weight of the asbestos fibre although this can be varied according to the characteristics of'the product desired. This oxidizing agent facilitates or hastens the cure of the binder'and adds to the strength of the product andv also converts the binder into a form insoluble by oil or water. It

also tends to produce a uniform curing,

throughout the mass during the curing 0 eration hereinafter described. It is to he noted that this reagent is put into the pulp before the formation of the sheet and not during the saturating and curing steps of are then hung up to dry in a dryin room of sufficient temperature to remove t e water. The sheet is then calendered to the desired thickness and the friction facings are then cut out of the sheet. The sheets are subjected to suflicient pressure in the calender to obtain as much tensile strength in the dry sheet as is feasible. The friction facings whether clutch rings or brake'linings are now ready for saturation. The saturating tank is filled with a binder. This bindermay consist of 94 percent of linseed oil, 6 percent of gilsonite in the solution in the oil thinned with gasoline to about 33 Baum gravity. The friction facings are then immersed while suspended on suitable rods in this binder solution for a period of half an hour. The friction facings are then removed and put in a closed steam oven and maintained at a temperature of about 200 F. to drive off the gasoline which gasoline may be recovered and saved. This steam treatment is preferably continued from two to three hours. The friction facings are then removed to a closed baking oven where they are subjected to a temperature of about 250 F., for a period of 'second closed baking oven and maintained at a temperature of 300 F. for twenty-four hours. The heat in both of the baking ovens is preferably dry heat. The friction facings are then removed from the second oven and sand papered to micrometer size and to get a smooth finish to the facing. The facings are now ready for use.

I have given above an illustration in which the process is actually carried out in commercial operation. It is to be understood that ;the temperature and length of treatment are subject to reasonable variations depending on the flexibility and strength required in the finished product. Also oils other than linseed oil may perhaps in certain cases be used and other asphalts substituted for gilsonite.

During the baking operation, the linseed oil, due to the presence of the air in the oven and also to the oxidizing agent of the sheet is oxidized to produce a tough hard binder. The solubility of the linseed oil in the gasoline before the baking treatments" ispractically 100% while after the baking treatments it 'is very materially reduced; and in fact the baking 0 eration may be so carried out as to make t e oil practically insoluble in the gasoline. It is to be noted that by means of the double saturation and double baking, a more efficient curing of the binder is obtained and the sheet can be impregnated with larger quantities of binder. This adds greatly to the tensile-strength and hardness I of the finished product. In order that the tensile strength of the friction facings made in this mannenmay be more clearly understood, I' submit the following table giving actual tests made on such friction facings:

The strength and hardness of the product made by this process is far inexcess, in fact from 1000 to 2000 lbs., upwards in tensile The facings are then taken strength, over that heretofore obtained from any unWoven saturated friction facing and is even stronger than a woven sheet. The hardness also is proportionately increased over the friction facings heretofore. made.

' It is to be noted that in the baking operation, the reaction develops autogenous heat or in other words exo-thermic and care must be taken to prevent the material from becoming so highly heated as to catch fire. This exo-thermic reaction results in the fact that the oxidation is of such a character as to generate heat in addition to that external- 1y applied. This exo-thermic reaction of oxidation is well known in other arts as for example in the manufacture of air blown asphalt from petroleum residuum.

I claim as my invention:

1. Aprocess of making a friction facing, of mixin asbestos pulp with an oxidizing agent and with comminuted graphite, forming sheets therefrom, cutting friction facings from the sheets, saturating the facings with a binder oil and. baking the friction comminuted graphite, forming unwoven sheets therefrom, cutting friction facings from such sheets and sub] ecting the friction facing to a saturation in a binder 011 and then baking.

3. A friction facing, the wearing surface of which consists essentially of unwoven asbestos fibre, a baked binder and graphite.

4. The process of making friction facings, consisting in incorporating with fibrous material a comminuted graphite, saturating the same in a binder and then baking thefacing.

5. The process of making friction facings,

consisting in incorporating with fibrous material a comminuted graphite, in saturating the facings with an oil, and in then baking said facings containing the comminuted graphite and the oil.

6. The process of making friction facings, consisting in mixing fibrous pulp with graphite and forming unwoven binder oil, and then baking the facing.

7. The process of making friction facings,

consisting in mixing asbestos with a comminuted graphite, saturating the asbestos with a binder oil and subjecting the saturated'mat'erial to heat treatment.

8. The process of making friction facings, consisting in mixing fibrous 'pulp with a comminuted graphite, forming sheets therefrom, saturating the sheet with a binder oil,

and subjecting the saturated sheets to heat.

treatment.

FREDERICK C. STANLEY.

sheets -therefrom, saturating the facing with a 

